The present invention relates to light modulators generally.
Various types of light modulators are known. These include, for example, Mach-Zehnder type modulators and electroabsorption modulators. The following literature references describe various Mach-Zehnder type modulators:
High-Speed Electrooptic Modulation in GaAs/GaAlAs Waveguide Devices, by Robert G. Walker, Journal of Lightwave Technology, Vol LT-5, No. 10, pp 1444-1453, October, 1987 and the references therein;
Broadband Y-branch electro-optic GaAs waveguide interferometer for 1.3 micrometers, by P. Buchmann et al, Applied Physics Letters, Vol 46, No. 5, pp 462-464 (1985);
Broad-Band Guided-Wave Electrooptic Modulators, by Richard A. Becker, The Journal of Quantum Electronics, Vol. QE-20, No. 7, July, 1984, pp 723-727;
The following product publications describe what is believed to be the state Mach-Zehnder optical modulators:
LC100 Series GaAs Optical Modulators for D.C. to 50 GHz, GEC-Marconi, Materials Technology, Caswell Towcester, Northamptonshire, U.K.
2.5 GHz, 8 and 18 GHz Integrated Optical Amplitude Modulators, GEC Advanced Optical Products, West Hanningfield Road, Great Baddow, Chelmsford, Essex, U.K.
The following reference shows an optical switch which employs a multimode interference coupler:
Novel 1xc3x97N and Nxc3x97N integrated optical switches using self-imaging multimode GaAs/AlGaAs waveguides by R. M. Jenkins et al., Applied Physics Letters, Vol 64 (6), Feb. 7, 1994, pp. 684-686.
The present invention seeks to provide an improved and exceedingly cost effective optical coupler.
There is thus provided in accordance with a preferred embodiment of the present invention a modulated light source module including a modulator disposed in a housing, a laser diode light source disposed in the housing and fiberlessly coupled to the modulator, and output optics operative to direct modulated light from the modulator into an optical fiber extending outwardly from the housing.
Further in accordance with a preferred embodiment of the present invention the modulator includes an input multi-mode interference coupler; an output multi-mode interference coupler, and first and second waveguides interconnecting the input multimode interference coupler and the output multi-mode interference coupler, the first and second waveguides having associated therewith electrodes for the application of voltage thereacross, thereby to vary the phase of light passing therealong.
Still further in accordance with a preferred embodiment of the present invention the modulator includes an input Y-junction splitter, an output Y-junction combiner, and first and second waveguides interconnecting the Y-junction splitter and the output Y-junction combiner, the first and second waveguides having associated therewith electrodes for the application of voltage thereacross, thereby to vary the phase of light passing therealong.
Additionally in accordance with a preferred embodiment of the present invention the laser diode light source is monolithically integrated with the modulator.
Preferably the laser diode light source is monolithically integrated with the modulator and occupy different regions of at least some of identical epitaxial layers.
Additionally or alternatively in accordance with a preferred embodiment of the present invention the laser diode light source is a discrete element which is mechanically mounted in a desired position with respect to said modulator.
Still further in accordance with a preferred embodiment of the present invention the laser diode light source is butted against an input to the modulator.
Alternatively the laser diode light source is coupled to an input to the modulator via a discrete lens.
Additionally in accordance with a preferred embodiment of the present invention the each of the laser diode light source and the modulator are mounted on parallel surface mountings, the parallel surface mountings include mutually facing surfaces which lie in parallel planes which are perpendicular to an optical axis of a light beam propagating from the laser diode light source towards the modulator via the lens.
Preferably the laser diode light source and the modulator are aligned by relative movement thereof in the parallel planes and are fixed in desired alignment by fixing the mutually facing surfaces together.
Further in accordance with a preferred embodiment of the present invention at least one of the laser diode light source and the modulator are mounted onto a support element by means of side mounting blocks which are fixed in position upon precise mutual alignment of the laser diode light source and the modulator.
Preferably the modulator is implemented in gallium arsenide.
There is also provided in accordance with a preferred embodiment of the present invention a method of producing a modulated light source including the steps of providing lator, fiberlessly coupling a laser diode light source to the modulator, and enclosing the modulator and the laser diode light source within a housing together with output optics operative to direct modulated light from the modulator into an optical fiber extending outwardly from the housing.
Further in accordance with a preferred embodiment of the present invention the step of fiberlessly coupling a laser diode light source to the modulator includes the steps of using at least one external manipulator, manipulating at least one of the modulator and the laser diode light source relative to the other such that the output beam of the laser diode enters the modulator with relatively low light loss, and fixing the modulator and the laser diode light source in desired relative positions independently of the external manipulator, and disengaging the at least one external manipulator from the modulated light source.
Still further in accordance with a preferred embodiment of the present invention the step of fixing the modulator and the laser diode light source in desired relative positions comprises fixedly attaching parallel surfaces attached to the modulator and to the laser diode light source to each other in desired relative orientations.
Preferably the step of fixing the modulator and the laser diode light source in desired relative positions includes employing side mounting blocks to fix at least one of the laser diode light source and the modulator in position upon precise mutual alignment of the laser diode light source and the modulator.